Method and a device for processing a solution, melt, suspension, emulsion, slurry or solids into granules

ABSTRACT

A classifying fluid bed granulator includes a granulation chamber including a fluidizing air chamber ( 7 ) with a bed floor ( 10 ), a ceiling ( 3   c ), an end wall ( 3   d ), and a feed inlet ( 5 ), a seed inlet ( 6 ), an air outlet ( 4 ) defined by walls ( 3   a   , 3   b ) and an outlet ( 9 ) for produced granules. The granulation chamber is divided into an agglomeration and seed control section ( 1 ) and a granulation and classification section ( 2 ), and the section ( 2 ) includes one or more consecutive compartments having an asymmetric design.

BACKGROUND OF THE INVENTION

The present invention relates to a method and a device for processing asolution, melt, suspension, emulsion, slurry or solids into granules ofa classified size.

Fluid bed granulation or fluidized bed granulation is a technique usedin particulation of melts, solutions, slurries, emulsions, suspensionsor solids, for instance in the fertilizer and food industries.

A fluid bed granulation process combines several sciences andtechnologies. To operate a fluid bed granulation plant properly,knowledge of melt and solution chemistry, crystallization properties,total mass- and energy balance, mass- and energy transport, particle-and granulometry balance, fluid dynamics and fluidization technology arerequired.

To design and operate these plants is difficult due to the fact that themass balance, energy balance and granulometry balance must be setcorrectly to give the right performance with regard to capacity andquality. Each of the balances can not be set independently as most ofthe control parameters available to operators and designers affect allthree balances. The balances expressed as a limited and simplified setof equations will also have several solutions, where the optimum or bestsolution depends on the chemical and physical properties of the productsystem, product quality and cost of utilities and other input factors.

Different salt systems have different solubilities and different heatsof crystallization. In fluid bed design, these differences give avariety of design parameters and settings for air flow and temperature,recycle flow and temperature, melt temperature and concentration. Themost important factor for the fluid bed granulation process is thecontrol of the liquid phase together with the overall energy balance andgranulometry balance through the particle growth and the production ofseed particles.

A seed particle is defined as a particle too large to be carried outwith the exhaust airflow through the granulator, large enough to preventbeing agglomerated with other particles, and smaller than the desiredproduct size.

In a conventional fluid bed granulation process, the size distributionof the produced granules has been controlled by recycling a certainfraction of undersized granules and crushed oversized granules to thegranulator. This eases the operation and the flexibility of the process,making it possible to handle various systems and granulometry, and stillbe able to control the conditions in the fluid bed (i.e., the liquidphase and the crystallization evaporation rate). The fact that afluidized bed granulator operates as a total mixed reactor has furthersupported the robust design and operational philosophy.

An excessive recycle stream, 0.5 to 2 times the product flow, carryingan excess of seed granules and mass flow, limits the influence of andsensitivity to other operating parameters. This has limited the interestin developing classifying granulators. Fluid bed granulation processesare sensitive to the number of seed particles produced, as agglomerationis undesired and should be avoided from a product quality and operatingstability point of view. Agglomeration creates particles with lowercrushing strength and it is difficult to use agglomeration to controlthe particle balance without increasing the recycle ratio to 3-7. Arobust design with an excess recycle stream as an important controlparameter, has been preferred by the industry. A low recycle flow isonly possible.

A classifying fluid bed granulator is defined as a granulator that isable to discharge the product that is the largest granule fractioncontained in the bed. The product continuously has a granule size whichis larger than the granules in the granulator. The efficiency of theclassification depends on the methods applied for classification and thesize differences handled by the bed. A classifying granulator will, in adynamic process, give a shorter retention time for the desired productfraction of large granules, thus giving a longer retention time for thesmaller granules, enabling them to grow more before reaching the productsize and be discharged. A classifying granulator will also be able toperform as an ideal plug flow reactor, given a feed of uniform seedmaterial. Screening and recycling of the granules in conventional fluidbed granulators is always done outside the bed as, for instance,described in U.S. Pat. No. 4,219,589.

Building mechanical screening and crushing into or close to the fluidbed granulator is described in DE 3248504-C2, but has-been seen as notadvantageous from an operational point of view.

However, U.S. Pat. No. 4,790,487 describes a continuous granulator wherescreening and recycling is done in an adjacent unit being a combinedscrew conveyor and fluid bed. The patent describes an apparatuscomprising a granulator body for continuously processing powderedmaterials into granules and a screw conveyor for discharging theproduced granules from the granulator body. The screw conveyor includesmeans for pneumatically classifying the produced granules while they arebeing conveyed. The patented principle will only be able to separate andrecycle the dust or fine particles from the discharge flow. Theclassification efficiency in the method is based on the difference inescape velocity between the large onsize granules and the dust fraction,and will not be able to separate 1-2 mm particles out of a masscontaining 1-5 mm particles. The bubble formation and slugging willcreate a flow of particles of all sizes between 1-5 mm back: to thegranulator.

Internal segregation effects in fluidized, spouted and moving beds havebeen described in several publications. The effects of air velocity andbubble breaking constructions inside the bed have produced documentedeffects achieving a particle size difference between top and bottom in asingle bed compartment. In “Powder Technology 98” (1998) 273-278, theeffect of horizontal baffles are described and documented.

The bed design with the internal baffles results in a single chamberhigh bed with a subsequent high pressure drop. The total bed movement isreduced by both the baffles and the geometry, and the bed achieves alower capacity because the heat and mass transfer requires turbulenceand particle movement.

Another disadvantage, making these principles less useful, is the lackof horizontal classification. With a vertical classification effectonly, size and shape of the granulator is limited in area to bed heightratio, and is therefore tested in a single chamber only. Horizontalbaffles placed in the single granulator chamber, as described in WO97/02887, is also seen as a practical disadvantage, as it gives lessfreedom to install spraying nozzles.

A significant disadvantage with a conventional but robust fluid bedprocess is the high investment costs in screens, crushers, dissolvingunits, dryers, coolers, intermediate storage and solid materialtransportation inside the plant. This requires large buildings andexpensive steel constructions to enable an operable layout. Eachmechanical and electrical item requires design, engineering,commissioning, spare parts, monitoring, maintenance, cleaning andattention from operators. In a corrosive environment due to salts andhumidity, the quality of materials increases the investment costfurther. The number of mechanical items increases the failure rate andrisk of expensive down time.

Furthermore, operation of these granulation plants requires frequentstops for maintenance of mechanical and electrical equipment andcleaning of process equipment. Recovery of washing water and extra spaceinside the plants for maintenance activities further increases the costfor constructing and operating such plants. Reducing the recycle flow byoptimizing the seed production and controlling the crystallization andsolidification process has given some competitive advantages for thebest processes.

Thermodynamically it is possible to design a fluid bed process with norecycling of cooled or heated granules outside the fluid bed. An optimumheat balance over a fluid bed granulator can be achieved by changing airtemperature or air flow. A relatively large air flow is required anywayfor the fluidization itself. The heat balance can alternatively besolved by internal cooling or heating in the fluid bed itself.

However, to operate a fluid bed granulation process without recyclingmaterial requires a control of the granule growth in a different waythan in conventional beds mentioned above. Granule growth and productgranulometry in conventional beds are a function of size distribution offeed or crushed recycled material, the feed to melt ratio, andclassifying effects in the fluid bed or granulator. Conventional bedshave low classifying efficiency, operating almost like, a total mixedflow reactor. The product from a total mixed reactor will consist of amix of fresh undersized feed and matured larger particles. Even with anideal plug flow reactor, the product is largely dependent on the sizedistribution of the feed or recycled material.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and adevice which are able to process a solution, melt, suspension, slurry,emulsion or solids into granules of a classified size.

It is another object of the present invention to provide a method and adevice which are able to process a solution, melt, suspension, slurry,emulsions or solids into granules in one stage, in one fluidized bed,without screening, recycling, crushing and dissolving.

Furthermore, it is another object of the present invention to provide amethod and a device mentioned above which reduce the investment cost fora fluid bed granulator unit, and increase the capacity when introducedin existing plants.

The inventors have developed a method and a device for fluid bedgranulation which are able to process a melt, solution, solid, emulsion,slurry or suspension into granules of a narrow size distribution.

The classifying fluid bed granulator according to the present inventioncomprises a granulation chamber including a fluidizing air chamber 7with a bed floor 10, a ceiling 3 c, an end wall 3 d, a feed inlet 5, aseed inlet 6, an outlet 4 defined by walls 3 a,3 b for air, and anoutlet 9 for produced granules. The granulation chamber is divided intoan agglomeration and seed control section (i.e., an agglomerationsection) 1, and a granulation and classification section (i.e., aclassification section) 2 where the section 2 consists of one or moreconsecutive compartments having an asymmetric design.

The method according to the present invention for fluid bed granulationof feed being a solution, slurry, melt, emulsion, suspension or solidsinto granules of a desired classified size, comprises that inlet seedparticles to be granulated with the feed are given a controlled size inan agglomeration and seed section ahead of a granulation andclassification section, and that the classification of the granules isperformed in asymmetric compartments in the granulation andclassification section.

The granulator consists of one or preferably several spray and particlegrowth compartments with an asymmetric design and with tilted (inclined)separation baffles which result in classification of particles in eachcompartment and transport of large particles towards the outlet andsmall particles towards the inlet of the bed.

The asymmetric design, obtained by tilting the separation baffles andsloping the bed floor, creates differentiations in fluidization air flowin various parts of the bed and within each compartment.

The classifying fluid bed granulator unit itself, according to thepresent invention, performs internally what the screens and recycle loopdo in a conventional granulation loop. In the classifying fluid bed, thegranules which are smaller than the desired product are given a longerresidence time inside the bed, until they have grown to the desiredproduct size. Thus, there will be no small particles which have to berecirculated. In a conventional bed, the smallest granules have to berecycled back to the bed to get a longer retention time. In theclassifying fluid bed the large particles will have a short residencetime. The conventional bed does not provide large particles with ashorter residence time, and small particles with a longer residencetime. Thus, there will be a higher fraction of too large particlesproduced in the bed. This together with the granule growth balancerequires a continuous crushing of oversize particles.

In the classifying fluid bed, a controlled crushing can can, however, beintroduced in the form of a rotor with variable speed placed in the seedand agglomeration control compartment. This will be required to produceenough seed material for the granulometry balance.

The dependence on the feed seed granulometry is reduced. From thegranulometry aspect it is basically the number of seed particles andenlargement factor which determine the capacity.

The effect of segregation in a sliding mass of inhomogeneous particlesis known but not utilized in a fluid bed granulator design. Thesegregation in a vibrated mass called percolation, where dust andsmaller particles fall down between the larger granules, is also notutilized. This effect is more pronounced when movement is low, and willin a fluid bed be prevented or reversed by the air flow.

Segregation in a sliding or moving mass is utilized in pan granulationand in some drum granulators, but the mass and energy balance for thesegranulation processes normally requires a well defined and large amountof temperature controlled recycle material.

An important features of the design is the asymmetry provided by thetilting baffle plates and/or the sloping of the floor. The higherfluidization velocity towards the outlet of the bed, combined with thesloped ceiling towards the outlet, produces a circular flow pattern bothin the total bed and between the tilted baffles. The higher air velocityand kinetic energy input on one side produces a higher bed level due tothe lower density. This results in an effect where small particles onthe top of the bed float back to the agglomeration and seed controlsection, and the largest particles float along the floor due to thecircular flow between the plates or inside each chamber, and an overallcirculating flow is produced.

Between compartments and over each plate, a stagewise classification isobtained by creating a high velocity bubble zone for the coarsematerial, and a low velocity zone for the smaller particles. With aninternal horizontal segregation in each compartment, a random exchangeof particles between compartments will give an overall classificationfrom compartment to compartment. In addition, the overall circular bedmovement will secure a movement of larger particles towards the outletalong the floor, and of fine particles back towards the inlet at the topof the bed. The invention will be further explained and envisaged in thefollowing figures and example.

The geometry of the baffles and shape of the classifying area must betailored to, fit the actual granulation system. The baffles provide amultistage classification system, with a certain efficiency over eachstage. The baffles divide the granulator into a series of stepsresembling a multistage reactor. The achieved effect resembles a plugflow and, combined with the controlled recycle of fine particles overthe top of the plates, gives a multiple stage classifying effect like ina distillation column. The size distribution of the product leaving thebed is clearly narrower than the total size distribution of the productcontained in the granulator.

The air flow direction at the upper portion of the fluidized area in theclassifying area transports the smaller particles towards the growtharea of the bed, where they function as seed material. The overall airflow above the top of the bed level, together with the mechanicaldesign, wind screens the granules and sends the smallest to thegranulation zone and allows the large particles to leave as product.

Provided a uniform size distribution of the feed to the granulator, theretention time distribution will also be narrowed, with a designaccording to the present invention.

There are various ways of providing seeding to a granulator withoutcrushing a part of the product. A pre-agglomeration or a small prillingtower has been proposed, as well as installing a grinder or crusherinside the bed. A rotor with a variable speed can be utilized to provideseed material and control the product particle size.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further explained and envisaged in the followingfigures and example.

FIG. 1 is a side view (in a reduced scale) of one design of theclassifying fluid bed granulator according to the present invention,with a sloped bed floor and tilted baffle plates.

FIG. 2 is a side view (in a reduced scale) of an alternative design ofthe classifying fluid bed granulator according to the present invention,with a horizontal bed floor, tilted baffle plates and a fluidized airchamber divided into compartments.

FIG. 3 is a schematic view illustrating the classification effects inthe classifying fluid bed granulator according to the present invention.

FIG. 4 is a geometrical sketch of how V-shaped baffles can be installedin the granulator according to the present invention.

FIG. 5 is a schematic view illustrating how V-shaped baffle plates willfurther enhance the effect of the baffles.

FIG. 6 is a side view of a pilot unit of the granulator according to thepresent invention.

FIG. 7 is a graph illustrating the classification efficiencycalculation.

FIG. 8 is a graph illustrating the results of the dynamic tests.

FIG. 9 is a graph illustrating the classification efficiencycalculation.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 show a fluid bed granulator which comprises a typicalagglomeration and seed control section (i.e., an agglomeration section)1, a granulation and classification section (i.e., a classificationsection) 2, an air pressure chamber 7, and a horizontal uphill-slopedbed floor 10. Section 2 contains tilted (inclined) baffle plates 12.Furthermore, the granulator consists of an inlet 5 for feeding the melt,solution, emulsion, slurry, solids or suspension into section 1, aninlet for seed material 6, an outlet 4 defined by walls 3 a,3 b fordischarging air, a ceiling 3 c, an end wall 3 d and an outlet 9 fordischarging produced granules of desired size. As illustrated in FIGS.1-3, each baffle plate 12 has a free upper edge (i.e., an upper edgethat is not adjoining a wall or another component so that there is a gapor open space above the free upper edge), and has a free lower edge(i.e., a lower edge that is not adjoining a wall or another component sothat there is a gap or open space below the free lower edge). Therefore,granules are able to travel over and under each baffle plate within thegranulator, as shown in FIG. 3.

In the agglomeration and seed control section 1, which may consist ofone or more consecutive compartments, the melt, suspension, slurry,solids or solution is sprayed onto the seed particles where itsolidifies creating agglomeration or layering. Necessary seed productioncan be done outside or inside the fluid bed by means of physicalcrushing.

The compartment(s) in section 1 may perform as a turbulent total mixedreactor(s), which is necessary to achieve high capacity of meltinjection without creating excess agglomeration and lump formation. Lowair velocity provides more agglomeration, reduces the dust formation,and reduces the carryover of dust with air exiting the bed 4. The totalload and air velocity in section 1 may in this way be used to controlthe seed production and granulometry of the whole bed. The sprayingtechnique may be with two-phase or one phase nozzles. Nozzle directionmay also vary depending on the individual properties between melt orsolution systems. The transport: of the largest particles from section 1to section 2 takes place along the floor 10, and is caused; by therotational driving force in the total bed due to the slope of the floor,the difference in fluidization air rate, and/or due to directionalnozzles in the bed floor. Some large particles are also carried over atthe top of the bed where the bubble breaking randomly sends particles inall directions. The larger particles are less affected by the horizontalair flow on the top of the bed, and will move to the compartment closerto the outlet easier than the smaller particles which will be taken bythe horizontal air flow back into the existing compartment or to thecompartment closer to the inlet.

The air velocities in the granulation and classification section 2 maybe higher than in the agglomeration and seed control section 1, and theair velocity should also be higher for each compartment towards theoutlet 9 as a requirement for fluidizing the increased particle size,but also as an important factor for the overall classification. A higherfluidization air velocity provides a higher air pressure in the bed anda higher level in the bed. The horizontal gradient in air and bedpressure gives an average horizontal air flow component in the bed,which provides a horizontal segregation. Smaller particles are blownback towards the agglomeration and seed control section 1. The airchamber 7 may comprise consecutive compartments. One way of achieving ahigher fluidization air velocity towards the outlet is to reduce thepressure drop over the bed floor 10 towards the outlet, or to increasethe pressure in the consecutive air compartments towards the outlet. Thepressure drop can be adjusted by the size or number of openings in theperforated bed floor.

The bed height will also affect the air velocity. A higher bed levelproduces a higher pressure drop and lower air flow for that area. Thiscan be achieved by the slope of the bed floor 10 as shown in FIGS. 1 and2. A higher air flow in chamber(s) in the granulation section 2 towardsthe outlet 9 gives a higher average level of material in the thesesections and compartments, and there will be a transport of smallerparticles from the upper zone 3 in these sections back to theagglomeration and seed control section 1. This effect is furtherenhanced by the free airflow zone 3 towards the air outlet 4.

Cooling, if required, is provided by low temperature fluidization air,and/or with internal cooling plates or tubes submerged horizontally orvertically within the fluidized material in the bed.

In the granulation and classification section 2, it is important tobreak or control the bubbles which are formed in a fluidized highdensity bed. These bubbles transport coarse material from the bottom tothe top of the bed. With the horizontal asymmetry in both air velocityand geometry, the bubbles 11 (as shown in FIG. 3) move horizontallytowards the tilted baffle or compartment wall where they change shape,leaving the coarse material as the bubbles rise along the baffle andbreak through the surface of the material contained in the bed. At thebreakthrough of the bubbles, the ejection of material gives a transportof fine material backwards and coarse material forward in the bed.

On the other side of the baffle, smaller particles will be increasinglyconcentrated in a downward movement. The lack of turbulence and lowerair velocity favors collection of small particles. The smaller particleswill be moving downwards, under the baffle and into the next chamber orsection. The distance from the lower end (free lower edge) of the baffleplate to the bed floor, should be tuned to achieve a stable circularmovement between the plates, and to achieve sufficient transport betweenthe chambers. The angle and shape of the baffle plates are important toachieve the right flow pattern. The transport of particles on both sidesof the baffle plate can further be improved by V-shaping the plate,making the transfer between chambers even better, as shown in FIGS. 4and 5.

The raising bubbles of coarse material in zone 3 transport coarsematerial up and over to the downward fine material zone 2 in the nextcompartment. In the same way, small particles in 2 will be transferredback to zone 3 in the previous compartment. At the top and bottom of thebed, below and above the baffles, a random movement pattern will secureexchange between the compartments.

EXAMPLE

This example shows test results achieved with a classifying fluid bedgranulator unit as shown in FIG. 6. The unit was operated with thefollowing parameters:

-   Material: Urea granules with a bulk density of 1000 kg/m³ Air-   velocity: 1.1-1.4 m/s-   Air temperature: Ambient, 20-22° Celsius-   Bed filling: 32.5-37 kg-   Bed slope, α: 6°-   Baffle slope β: 15°.

Typical size distribution of the material in the test bed is shown inTable 1:

TABLE 1 Typical size distribution in test bed Above 6 mm 1% Between6.3-4.5 mm 9% Between 4.5-3.5 mm 28%  Between 3.5-2.5 mm 49%  Between2.5-1.6 mm 11%  Between 1.6-1.0 mm 2% Between 1.0-0.0 mm 0%

The tests have been performed with the aim of finding the most effectivedesign, and a classification efficiency measurement has been introduced.The measurement calculates how the D50 of the outlet product compares tothe D50 for the whole content in the bed. If the D50 of the outlet isequal to the total bed D50, the classification efficiency is 0%, whichmeans there is no effect as compared to a total mixed bed. If the D50 ofthe outlet is equal to D90 of the whole bed, the classificationefficiency is 80%. The D50 is the granule diameter which splits the massinto 50% of the granules smaller than this diameter and subsequently 50%of the granules larger. The D90 is (in the same way) the granulediameter which splits the mass into 90% of the granules smaller thanthis diameter, and subsequently 10% of the granule mass larger thisdiameter.

FIG. 7 illustrates the classification efficiency calculation.

The bed efficiency has been tested both in dynamic and staticsituations, static meaning that the bed has been filled and operatedwithout any discharge or feed of material. Sampling of the outlet hasbeen done only to check that steady state has been achieved.

The dynamic tests were simulated by taking out product at the outlet andrefeeding it to the inlet. The load has been calculated as retentiontime. Simulated retention time of 10 minutes has been used in thedynamic testing.

FIGS. 8 and 9 illustrate the results of the tests. FIG. 8 shows how thesize distribution curve of the outlet changes compared to the totalcontent of the bed. FIG. 9 shows the same for the accumulated sizedistribution curve.

Table 2 shows a representative extract of the classification efficiencyresults. The best results are achieved with three baffles tilted 15degrees, and a bed sloped 6 to 10 degrees. Positive results are,however, achieved with several features as indicated in the table.

TABLE 2 Test results Number Slope of Slope of Load as Test of Baffles inBed in Ceiling retention Classification No. Baffles degrees degreesposition time efficiency 0 One As for Bed 0 No ceiling No load  0% 5 ″ ″0 Ceiling down No load 13% 3 ″ ″ 4 Ceiling down 30 min. 36% 4 ″ ″ 4Ceiling down 10 min. 48% 5 ″ ″ 4 Ceiling down No load 50% 6 ″ ″ 6Ceiling down 10 min. 54% 7 ″ ″ 10 Ceiling down 10 min. 45% 8 Three  4 4Ceiling down 10 min. 72% 9 ″ 15 4 No ceiling 10 min. 82% 10 ″ 15 4Ceiling down 10 min. 64%

Test number 10 was done with a higher bed level, which created a changein fluidization conditions towards the outlet of the bed due torestrictions.

The present invention will open for granulation without screening andrecycling granules outside the bed, given only a suitable seedingprocess or a feed of seed material.

As an example, the fluid bed will be perfect for fattening or postgranulation of smallprilled particles of 1-2 mm to larger granules of3-7 mm.

1. A classifying fluid bed granulator comprising: a granulation chamberhaving an agglomeration section and a classification section, saidgranulation chamber including: a bed floor; a ceiling above said bedfloor; an end wall between said bed floor and said ceiling; a feedmaterial inlet at said agglomeration section; a seed inlet at saidagglomeration section; an air outlet; and a granule outlet at saidclassification section such that said classification section is locatedcloser to said granule outlet than is said agglomeration section,wherein a bed floor of said classification section is sloped upwardstoward said granule outlet so as to form an angle with a horizontalplane, and an entirety of said bed floor of said granulation chamber issloped upwards toward said granule outlet so as to form an angle withthe horizontal plane; and a fluidizing air chamber for supplyingfluidizing air to said granulation chamber; wherein said classificationsection includes at least one asymmetrically-shaped compartment, each ofsaid at least one asymmetrically-shaped compartment including a baffleplate having a free lower edge closest to said bed floor and having afree upper edge opposite said lower edge and closest to said ceiling. 2.The classifying fluid bed granulator of claim 1, wherein said baffleplate of each of said at least one asymmetrically-shaped compartment isinclined at an angle with respect to the horizontal plane.
 3. Theclassifying fluid bed granulator of claim 2, wherein said baffle plateof each of said at least one asymmetrically-shaped compartment isinclined at an angle other than 90° with respect to the horizontalplane.
 4. The classifying fluid bed granulator of claim 2, wherein saidbaffle plate of each of said at least one asymmetrically-shapedcompartment is inclined at an angle of one of 4° and 15° with respect tothe horizontal plane.
 5. The classifying fluid bed granulator of claim2, wherein said baffle plate of each of said at least oneasymmetrically-shaped compartment comprises a V-shaped baffle plate. 6.The classifying fluid bed granulator of claim 2, wherein said baffleplate of each of said at least one asymmetrically-shaped compartment isinclined at an angle other than 90° with respect to the horizontalplane.
 7. The classifying fluid bed granulator of claim 1, wherein saidbed floor is sloped upwards toward said granule outlet so as to form anangle in a range of 6° to 10° with the horizontal plane.
 8. Theclassifying fluid bed granulator of claim 1, wherein said agglomerationsection includes a plurality of consecutively-arranged compartments. 9.The classifying fluid bed granulator of claim 1, wherein said fluidizingair chamber includes a plurality of consecutively-arranged aircompartments.
 10. The classifying fluid bed granulator of claim 1,wherein said bed floor is arranged between said granulation chamber andsaid fluidizing air chamber, said bed floor including perforationshaving different sizes so as to provide a different amount of air fromsaid fluidizing air chamber to said agglomeration chamber than from saidfluidizing air chamber to said classification chamber.
 11. Theclassifying fluid bed granulator of claim 1, wherein said granule outletis located at said end wall, and said end wall slopes inwardly towardsaid seed inlet and said feed material inlet.
 12. The classifying fluidbed granulator of claim 11, wherein said ceiling slopes downwardlytoward said granule outlet.
 13. The classifying fluid bed granulator ofclaim 1, wherein said classification section of said granulation chamberincludes a plurality of asymmetrically-shaped and consecutively-arrangedcompartments, said baffle plate of each of said compartments beinginclined with respect to the horizontal plane at an angle other than90°.
 14. The classifying fluid bed granulator of claim 1, wherein a bedfloor of said classification section is sloped upwards toward saidgranule outlet so as to form an angle in a range of 4° to 10° with thehorizontal plane.
 15. The classifying fluid bed granulator of claim 1,wherein said baffle plate of each of said at least oneasymmetrically-shaped compartment comprises an inclined flat baffleplate.
 16. A classifying fluid bed granulator comprising: a granulationchamber having an agglomeration section and a classification section,said granulation chamber including: a bed floor; a ceiling above saidbed floor; an end wall between said bed floor and said ceiling; a feedmaterial inlet at said agglomeration section; a seed inlet at saidagglomeration section; an air outlet; and a granule outlet at saidclassification section such that said classification section is locatedcloser to said granule outlet than is said agglomeration section; and afluidizing air chamber for supplying fluidizing air to said granulationchamber; wherein said classification section includes at least oneasymmetrically-shaped compartment, each of said at least oneasymmetrically-shaped compartment including a baffle plate having a freelower edge closest to said bed floor and having a free upper edgeopposite said lower edge and closest to said ceiling, and wherein eachof said at least one asymmetrically-shaped compartment is defined bysaid baffle plate inclined at an angle with respect to a horizontalplane and by said bed floor sloping upwards toward said granule outletso as to form an angle with the horizontal plane.
 17. A method of fluidbed granulation, comprising: supplying a feed material into anagglomeration section of a granulation chamber, the feed materialcomprising one of a solution, a slurry, a melt, an emulsion, asuspension, and solids; supplying seed particles into the agglomerationsection of the granulation chamber; granulating the seed particles withthe feed material in the agglomeration section so as to form granuleshaving a controlled size; and classifying the granules according to sizein a classification section of the granulation chamber, theclassification section located downstream of the agglomeration sectionand including a granule outlet and at least one asymmetrically-shapedcompartment, each of the at least one asymmetrically-shaped compartmentincluding a baffle plate having a free lower edge closest to a bed floorof the classification section and having a free upper edge opposite thelower edge and closest to a ceiling of the classification section, saidclassifying of the granules comprising supplying fluidizing air to thegranulation chamber so as to classify the granules by transporting thegranules over the free upper edge and under the free lower edge of thebaffle plate of each of the at least one asymmetrically-shapedcompartment, wherein said supplying of the fluidizing air to thegranulation chamber comprises supplying the fluidizing air so as toproduce a rotating flow of the granules in the granulation chamber,wherein the rotating flow is produced by at least one of: providing anupwardly-sloped bed floor toward the granule outlet and providing an endwall at the granule outlet inclined inwardly toward the agglomerationsection; varying the supply of fluidizing air such that a fluidizing airvelocity in the classification section is higher than a fluidizing airvelocity in the agglomeration section; and supplying the fluidizing airusing directional nozzles in a bed floor of the granulation chamber. 18.The method of claim 17, wherein the classification section includes aplurality of asymmetrically-shaped compartments, each of thecompartments being including an inclined baffle plate for separating thecompartments.
 19. The method of claim 18, wherein the granule outlet isprovided at an end of the classification section farthest from theagglomeration section, said supplying of the fluidizing air to thegranulation chamber comprising supplying the fluidizing air such that afluidizing air velocity in one of the compartments of the classificationsection closest to the granulate outlet is higher than a fluidizing airvelocity in one of the compartments of the classification sectionfarthest from the granule outlet.
 20. The method of claim 17, whereinsaid supplying of the fluidizing air to the granulation chambercomprises supplying the fluidizing air such that a fluidizing airvelocity in the classification section is higher than a fluidizing airvelocity in the agglomeration section, whereby granules smaller than adesired size are transported back toward the agglomeration section ofthe granulation chamber.
 21. The method of claim 17, wherein the bedfloor of the classification section is sloped upwards toward the granuleoutlet so that the bed floor forms an angle with a horizontal plane.